Patient-specific guide for partial acetabular socket replacement

ABSTRACT

A device for partial acetabular replacement includes a patient-specific acetabular guide. The acetabular guide has a first surface configured to nestingly mate in only one position to the patient&#39;s acetabulum. The acetabular guide includes a patient-specific guiding formation configured to guide a cutting tool to remove damaged tissue from a defect of the patient&#39;s acetabulum and prepare a patient-specific implantation slot corresponding to the defect after removal of the damaged tissue. A patient-specific partial acetabular implant can be configured to nestingly mate with the patient-specific implantation slot.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 12/893,306, filed Sep. 29, 2010. The entiredisclosure of the above application is incorporated herein by reference.

INTRODUCTION

The present teachings provide a patient-specific guide and an associatedimplant and methods for preparing the acetabulum to receive a partialacetabular socket replacement. The patient-specific guide and implantare prepared preoperatively for the specific patient based on medicalscans of the relevant anatomy of the patient.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

The present teachings provide a device for partial acetabularreplacement that includes a patient-specific acetabular guide. Theacetabular guide has a first surface configured to nestingly mate inonly one position to the patient's acetabulum. The acetabular guideincludes a patient-specific guiding formation configured to guide acutting tool to remove damaged tissue from a defect of the patient'sacetabulum and prepare a patient-specific implantation slotcorresponding to the defect after removal of the damaged tissue. In someembodiments, a patient-specific partial acetabular implant can beconfigured to nestingly mate with the patient-specific implantationslot.

The present teachings also provide a method for a partial socketreplacement. The method includes mounting a patient-specific acetabularguide on an acetabulum of a patient and guiding a cutting tool through apatient-specific bore of the acetabular guide. The acetabular guide isconfigured to mate to the patient's acetabulum in only one position andthe patient-specific bore of the acetabular guide is configured tooverlay a defect in the acetabulum of the patient. The method includesremoving damaged tissue of the defect, and forming a patient-specificimplantation slot by removing the damaged tissue. A patient-specificpartial acetabular implant can be configured to nestingly mate with thepatient-specific implantation slot.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

FIG. 1 is an exploded environmental perspective view of apatient-specific guide according to the present teachings;

FIG. 2 is another exploded environmental perspective view of thepatient-specific guide of FIG. 1;

FIG. 3 is an environmental perspective view of the patient-specificguide of FIG. 1;

FIG. 4 is an environmental sectional view of the patient-specific guideof FIG. 1;

FIG. 4A is an environmental sectional view of a patient-specific guideaccording to the present teachings;

FIG. 5 is an exploded environmental view of an implant according to thepresent teachings;

FIG. 6 is an environmental view of the implant of FIG. 5;

FIG. 7 is an environmental view of an inverse patient-specific guideshowing how to make a patient-specific allograft implant from allografttissue according to the present teachings;

FIG. 7A is a patient-specific implant made from allograft tissue usingthe inverse patient-specific guide of FIG. 7; and

FIGS. 7B-7D are snapshot diagrams of extracting the allograft implant ofFIG. 7A using the inverse patient-specific guide of FIG. 7.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Exemplary embodiments will now be described more fully with reference tothe accompanying drawings.

The present teachings generally provide a patient-specific (custom)guide, and associated implant and method for partial arthroplasty,including partial acetabular socket replacement, partial glenoid socketreplacement or other similar procedure. More specifically, the presentteachings provide a patient-specific guide for the acetabulum of thepatient, when the acetabulum includes a defect that can be corrected bya partial socket replacement or a partial implant.

Generally, patient-specific devices can be designed preoperatively usingcomputer-assisted image methods based on three- or two-dimensionalimages of the patient's knee anatomy reconstructed from MRI, CT,ultrasound, X-ray, or other three- or two-dimensional medical scans ofthe patient's anatomy and in some cases complemented with digitalphotography methods and/or anthropometry databases. Various CAD programsand/or software can be utilized for three-dimensional imagereconstruction, such as, for example, software commercially available byMaterialise USA, Plymouth, Mich.

Various alignment guides and pre-operative planning procedures aredisclosed in commonly assigned and co-pending U.S. patent applicationSer. No. 11/756,057, filed on May 31, 2007, U.S. patent application Ser.No. 12/211,407, filed Sep. 16, 2008; U.S. patent application Ser. No.11/971,390, filed on Jan. 9, 2008, U.S. patent application Ser. No.11/363,548, filed on Feb. 27, 2006; U.S. patent application Ser. No.12/025,414, filed Feb. 4, 2008, U.S. patent application Ser. No.12/571,969, filed Oct. 1, 2009, and U.S. patent application Ser. No.12/955,361, filed Nov. 29, 2010. The disclosures of the aboveapplications are incorporated herein by reference.

In the preoperative planning stage for a partial socket replacement,imaging data of the relevant anatomy of a patient can be obtained at amedical facility or doctor's office, using one of medical imagingmethods described above. The imaging data can include, for example,various medical scans of a relevant joint portion or other relevantportion of the patient's anatomy, as needed for joint modeling and,optionally, for implant alignment axis determination or for otheralignment purposes. The imaging data thus obtained and other associatedinformation can be used to construct a three-dimensional computer imageof the joint or other portion of the anatomy of the patient.

According to the present teachings, the patient-specific guides andimplants are generally configured to match the anatomy of a specificpatient and are generally formed using computer modeling based on thepatient's reconstructed three-dimensional anatomic image. Thepatient-specific guides have an engagement surface that is made toconformingly contact and match a three-dimensional image/model of thepatient's bone surface (with or without cartilage or other soft tissue),by the computer methods discussed above. In this respect, apatient-specific guide can nestingly mate with the corresponding bonesurface (with or without articular cartilage) of the specific patient inonly one position.

According to the present teachings, the patient-specific guide caninclude a custom-made (patient-specific) guiding formation, such as, forexample, a guiding bore for guiding a joint preparation tool, such as areamer, cutter, broach, mill, drill or other cutting tool, according tothe pre-operative plan for the patient. In some embodiments, the guidingformation can have a patient-specific size and shape configured duringthe preoperative plan for the patient to guide a milling tool, a reamer,a broach or other cutting tool, as discussed below. The preoperativeplan can include planning for bone or joint preparation, includingextent and area for defect removal, by milling, reaming, broaching orother cutting method, as well as implant selection and fitting.

The patient-specific guide described herein can be manufactured byvarious stereolithography methods, selective laser sintering, fuseddeposition modeling or other rapid prototyping methods. Thepatient-specific guide can be made of any biocompatible material,including metal, metal alloys or plastic. Generally, thepatient-specific guide is disposable and made of lightweight materials,including polymers. The patient-specific implant can be made of anybiocompatible materials, including metals and alloys. Thepatient-specific guide, implant and associated tools can be sterilizedand shipped to the surgeon or medical facility in a kit for a specificpatient and surgeon for use during the surgical procedure.

Referring to FIGS. 1-6, a patient-specific acetabular guide 100 forpreparing an acetabulum to receive a partial acetabular implant 300(partial acetabular socket replacement) is illustrated. As shown in FIG.1, the acetabulum of the pelvis of the patient includes an articularcartilage 84 and an acetabular fossa 83 in the acetabulum or acetabularsocket 80. A representative defect, such as damaged cartilage, isillustrated at 82. The patient-specific acetabular guide 100 is designedduring the preoperative plan of the patient for the specific patient.The patient-specific acetabular guide 100 is configured to guide acutting tool 200 to mill, burr or otherwise remove the damaged tissue ofthe defect 82 and prepare the acetabulum 80 for receiving a partialacetabular implant 300. The cutting tool 200 can include a handle 202and a cutting portion or cutting shaft 204, as shown in FIGS. 1 and 2.The partial acetabular implant 300, shown in FIGS. 5 and 6, is alsodesigned during the preoperative plan in coordination with thepatient-specific acetabular guide 100. As described below, the partialacetabular implant is also patient-specific, although non customimplants can be used, if desired, by selecting an appropriate size andshape from a non-custom database during the preoperative planning stage.

With continued reference to FIGS. 1-4, the acetabular guide 100 can beformed as a shell having a curved three-dimensional surface 102 (orfirst surface 102) and bounded by an opposite substantially planarsecond surface 104. The first surface 102 is patient-specific anddesigned to nestingly mate with the patient's acetabulum 80, includingthe articular cartilage 84 and the acetabular fossa 83 only in oneposition, as shown in FIGS. 3 and 4. In this regard, the patient'sacetabulum 80 provides reference landmarks, including, for example, thetransition or boundary between the articular cartilage 84 and theacetabular fossa 83 of the specific patient. The acetabular guide 100includes a patient-specific guiding formation 106 in the form of athrough slot or bore that extends between first and second openings 108and 110 on the first and second surfaces 102, 104 of the acetabularguide 100, as shown in FIG. 4. In some embodiments, the second surface104 may be omitted such that the acetabular guide 100 is in the form ofan open shell and the first opening 108 is the only opening of theguiding formation 106.

The guiding formation 106 is designed during the preoperative plan suchthat when the acetabular guide 100 can be seated in a unique position inthe acetabulum 80 of the patient, the guiding formation 106 can providea guiding surface for guiding the cutting portion 204 of the cuttingtool 200 to remove the damaged cartilage associated with the defect 82.Accordingly, the patient-specific acetabular guide 100 and guidingformation 106 stabilize and guide the cutting tool 200 intraoperatively,enabling the surgeon to remove the damaged tissue associated with thedefect 82 and/or other surrounding or underlying tissue in aconservative manner, as determined according to the preoperative planwith the approval of the surgeon. In this regard, the procedure canminimize tissue removal and conserve healthy patient tissue.

Referring to FIG. 4A, another embodiment of the acetabular guide 100Awith a depth stop or depth control feature is illustrated. Theacetabular guide 100A is in other respects similar to the acetabularguide 100, and the description of features common to those of theacetabular guide 100 is not repeated. The depth control feature of theacetabular guide 100A can be, for example, a three dimensional depthcontrol surface 103 extending from the planar second surface 104 of theacetabular guide 100A. The depth control surface 103 is configured tomate with a corresponding outer surface 203 of a distal portion 201 of ahandle 202 of a cutting tool 200A, similar in other respects to thecutting tool 200, as shown in FIG. 4A. The position and location of thedepth control surface 103 relative to the acetabular guide 100A isdetermined during the preoperative plan for the patient such that whenthe outer surface 203 of the handle 202 abuts the depth control surface103, defect removal and/or cutting by the cutting tool 200A does notexceed a predetermined cutting depth.

Using the cutting tool 200 (or 200A) and acetabular guide 100 (Or 100A),an implant-receiving site 86 is cut, milled or otherwise prepared in theacetabulum 80 of the patient for receiving the partial acetabularimplant 300, as shown in FIGS. 5 and 6. The implant-receiving site canbe a blind bore formed by removing the defect 82 and having apatient-specific wall 88 that is substantially an envelope of removeddefect 82. The acetabular implant 300 can be patient-specific andinclude a peripheral wall 304 configured to engage the wall 88 of theimplant-receiving site or slot 86. The partial acetabular implant 300includes an outer (articulating) surface 302 configured to continuouslytransition to the health portion of the articular cartilage 84, replacethe damaged cartilage 82 (FIG. 1) and re-create a patient-specificcontinuous articular cartilage surface without a defect. The partialacetabular implant 300 can include one or more anchoring elements 306,such as pegs, keels, pins or other protrusions, extending from theacetabular implant opposite to the outer surface 302 for anchoring theimplant into the acetabulum 80.

It should be appreciated that the wall 88 of the patient-specificimplant-receiving site 86 and the peripheral wall 304 of the implant 300can either follow and match the outline of the original defect 82 or canfollow and match a de-burred or smoother envelope of the defect 82. Theacetabular implant 300 can be made of any biocompatible materialincluding, for example, pyrocarbon or cobalt chromium alloy with apolished outer surface 304 for articulation with the femoral head of thejoint. Additionally, the acetabular implant can be made of allografttissue, as discussed below in reference to FIGS. 7 and 7A.

Intraoperatively, the patient-specific acetabular guide 100 is mountedon the patient's acetabulum 80 in a unique position determined by thepatient's acetabular geometry, which is referenced by the first surface102 of the acetabular guide, as shown in FIGS. 3 and 4. By design,during the preoperative plan of the patient, the patient-specificguiding formation 106 is configured to be aligned with and overlay thedefect 82 when the acetabular guide 100 is seated on the acetabulum. Acutting tool 200 can be guided by the guiding formation 106 to removethe damaged tissue of the defect 82 and create the implantation site 86for implanting the partial acetabular implant 300. The acetabularimplant 300 is then inserted into the implantation site 86 and replacesthe damaged tissue of the defect 82.

Example embodiments are provided so that this disclosure is thorough,and fully conveys the scope to those who are skilled in the art.Numerous specific details are set forth such as examples of specificcomponents, devices, and methods, to provide a thorough understanding ofembodiments of the present disclosure.

In some embodiments, the partial acetabular implant can be made ofallograft tissue. An exemplary partial patient-specific allograftimplant 300A (or allograft implant 300A, for short) is illustrated inFIG. 7A. Similarly to the partial acetabular implant 300 of FIG. 5, theallograft implant 300A has a peripheral wall 304 configured to engagethe wall 88 of the implant-receiving site or slot 86. The allograftimplant 300A includes an outer (articulating) surface 302 configured tocontinuously transition to the health portion of the articular cartilage84, replace the damaged cartilage 82 (FIG. 1) and re-create apatient-specific continuous articular cartilage surface without adefect.

To extract a patient-specific allograft from allograft tissue, an“inverse” acetabular guide 400 can be used as a guide. The inverseacetabular guide 400 is configured during the preoperative plan of thepatient for extracting wherein a patient-specific implant, i.e., theallograft implant 300A, from allograft tissue. The inverse acetabularguide 400 can be shell-like in shape with a curved surface 401 thatengages an allograft tissue (such as a cadaveric acetabulum) 80A. Anexternal protrusion 404 is defined by a curved guiding slot 402 throughthe inverse acetabular guide 400 and is connected to the acetabularguide through a neck portion 406. The guiding slot 402 and protrusion404 are patient-specific and designed and configured during thepreoperative plan for the patient to trace the shape and size of theperipheral wall 304 of the allograft implant 300A. The guiding slot 402can guide the cutting tool 200 along the guiding slot 402 and around theprotrusion 404, as shown in FIGS. 7 and 7A-7C, to cut the allograftportion for the allograft implant 300A having a peripheral wall 304, butstill attached to the allograft issue 80A along an uncut portioncorresponding to the neck portion 406 of the protrusion 404. The inverseacetabular guide 400 can then be removed and the allograft implant 300Acan be separated from the allograft tissue by cutting through anyremaining uncut portion.

It will be apparent to those skilled in the art that specific detailsneed not be employed, that example embodiments may be embodied in manydifferent forms and that neither should be construed to limit the scopeof the disclosure. In some example embodiments, well-known processes,well-known device structures, and well-known technologies are notdescribed in detail. Accordingly, individual elements or features of aparticular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

What is claimed is:
 1. A method for a partial socket replacementcomprising: mounting a patient-specific acetabular guide on anacetabulum of a patient, wherein the acetabular guide is configured tomate to the patient's acetabulum in only one position; guiding a cuttingtool through a patient-specific bore of the acetabular guide, whereinthe patient-specific bore of the acetabular guide is configured tooverlay a defect in the acetabulum of the patient; removing damagedtissue of the defect; forming a patient-specific implantation slot byremoving the damaged tissue, engaging a patient-specific inverseacetabular guide to allograft tissue; guiding a cutting tool along aguiding slot of the patient-specific inverse acetabular guide, theguiding slot configured during the preoperative plan to mate with a wallof the patient-specific implantation slot; and extracting apatient-specific partial acetabular implant from the allograft tissue;and implanting the patient-specific partial acetabular implant in thepatient-specific slot, wherein the implant is the allograft tissueimplant.
 2. The method of claim 1, wherein the partial acetabularimplant has a peripheral surface configured to mate with a wall of thepatient-specific implantation slot.
 3. The method of claim 2, whereinthe partial acetabular implant has an outer surface configured to becontinuous with a surrounding cartilage after implantation.
 4. Themethod of claim 1, further comprising anchoring the patient-specificpartial acetabular implant in the acetabulum using an anchoring element.5. The method of claim 1, wherein the acetabular guide has a firstcurved three-dimensional surface configured to nestingly mate in onlyone position to the patient's acetabulum, and a second planar surfaceopposite the first surface, and wherein the bore is an open boreextending between the first and second surfaces.
 6. The method of claim5, further comprising controlling a depth of the patient-specificimplantation slot.
 7. The method of claim 6, wherein controlling a depthof the patient-specific implantation slot includes engaging athree-dimensional depth control surface of the acetabular guide to acorresponding outer surface of a distal portion of a handle of thecutting tool.
 8. The method of claim 7, wherein the depth controlsurface extends from the planar second surface of the acetabular guide.9. A method for a partial socket replacement comprising: mounting apatient-specific acetabular guide on an acetabulum of a patient, whereinthe acetabular guide has a first curved three-dimensional surfaceconfigured to nestingly mate to the patient's acetabulum, including theacetabulum's articular cartilage and acetabular fossa in only oneposition; guiding a cutting tool through a patient-specific bore of theacetabular guide, wherein the patient-specific bore passes through thefirst surface of the acetabular guide and is configured to overlay adefect in the acetabulum of the patient; removing damaged tissue of thedefect; forming a patient-specific implantation slot; and controlling adepth of the patient-specific implantation slot by the acetabular guidephysically constraining the cutting tool from advancing further into theacetabulum.
 10. The method of claim 9, wherein the acetabular guide hasa second planar surface opposite the first surface, and wherein the boreis an open bore extending between the first and second surfaces.
 11. Themethod of claim 10, wherein controlling a depth of the patient-specificimplantation slot includes engaging a three-dimensional depth controlsurface of the acetabular guide to a corresponding outer surface of adistal portion of a handle of the cutting tool.
 12. The method of claim11, wherein the depth control surface extends from the planar secondsurface of the acetabular guide.
 13. The method of claim 9, furthercomprising implanting a patient-specific partial acetabular implant inthe patient-specific implantation slot.
 14. The method of claim 13,wherein the partial acetabular implant has a peripheral surfaceconfigured to mate with a wall of the patient-specific implantationslot.
 15. The method of claim 14, wherein the partial acetabular implanthas an outer surface configured to be continuous with a surroundingcartilage after implantation.
 16. The method of claim 13, furthercomprising anchoring the patient-specific partial acetabular implant inthe acetabulum using an anchoring element.
 17. A method for a partialsocket replacement comprising: mounting a patient-specific acetabularguide on an acetabulum of a patient, wherein the acetabular guide has afirst curved three-dimensional surface configured to nestingly mate tothe patient's acetabulum, including the acetabulum's articular cartilageand acetabular fossa in only one position, and a second planar surfaceopposite the first surface; guiding a cutting tool through apatient-specific bore of the acetabular guide, wherein thepatient-specific bore extends through the first and second surfaces ofthe acetabular guide and is configured to overlay a defect in theacetabulum of the patient; removing damaged tissue of the defect;forming a patient-specific implantation slot; and controlling a depth ofthe patient-specific implantation slot by the acetabular guidephysically constraining the cutting tool from advancing further into theacetabulum.